BIOL100 Study Guide - Midterm Guide: Polyploid, Gene Flow, Gastrulation

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Published on 14 Sep 2015
Department
Course
Professor
Bio Review
Lecture 9
Taxonomy-Naming and classifying life
Kingdom-Animalia
Phylum- Chordata
Class- Mammalia
Order-Carnivoria
Family- Felidae
Genus- Panthera
Species- pardus
Darwin’s Two Big Ideas
1.Evolution
2.Natural Selection- Mechanism for
evolution
-Need for variation
-Arguably the most important mechanism for evolution
-“decent with modification”
Darwin’s Evidence for Evolution
1. Artificial selection- species can change *dogs and cats*
2. Fossil Record- Species have changed *fossil examination*
3. Biogeography- Many islands have endemic species that are closely related to species of
nearby islands where ancestors may have come from a mainland
4. Homology- Similarity in plan, body structures *forelimbs of mammals*
5. Classification- Linnaeus’ filing system = Darwin believed this represented common ancestry
6. Rudimentary/vestigial organs- organs or structures that have no apparent purpose *snakes
have pelvic bones*
7. Embryology- Embryos of different species appear similar *humans and chick embryos*
Convergent evolution
-The evolution of similar or analogous features in distantly related groups
-Analogous traits arise when groups independently adapt to similar environments in different
ways
-Does not provide info about ancestry
Natural Selection *OBSERVATIONS*
1. There is a difference in phenotypes for most characters in a population
2. There traits come from the parents
3. Overproduction of offspring is frequently seen in nature
4. Only “lucky” few offspring will mature and reproduce
Natural Selection- Cautions
1. Survival of the fittest- evolution operates on populations
2. Only heritable traits are passed on
3. May be suitable for one environment
Natural Selection
Individual vs Population vs Species
Individuals= single organism
Populations= a localized group of individuals that belong to the same species
Species= a group of organisms that possess similar characteristic and can interbreed
Genetic variations contribute to evolution
Microevolution is a change in allele frequencies in a population
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-Population genetics *sources of genetic variation & changes in allele frequency*
Sources of Genetic Variation
1. Mutation
a) Point Mutations
b) Alterations of gene number or sequence
2. Sexual Reproduction
a) Crossing Over
b) Independent assortment
c) Fertilization
Three major factors alter allele frequency
-Genetic Drift
-Gene Flow
-Natural Selection
Hardy Weinberg
Gene pool- population’s genetic makeup, consisting of alleles at every locus in all members of
the population
P2+2pq+q2= 1
Conditions
1. No mutations 2. Random mating 3. No natural selection 4.Large population size 5. No
gene flow
Genetic Drift
Describes how allele frequencies fluctuate unpredictably from one generation to the nexr
Tends to reduce genetic variation though losses of alleles
1. Genetic Drift is significant in small populations
2. Causes allele frequencies to change at random
3. Can lead to loss of genetic variation *think of lego video Ryan showed*
4. Can cause harmful alleles to become fixed
Gene Flow
Consists of the movements of alleles among populations
Alleles can be transferred through the movement of fertile individuals or gametes
Gene flow tends to reduce differences between populations over time
Natural Selection
Relative fitness is the contribution and individual makes to the gene pool of the next
generation, relative to the contributions of other individuals
Selection favours certain genotypes by acting on the phenotypes of certain organisms
*Sneaky fucker example. Aggressive males fight and the weaker male comes in and mates
while the other males are busy*
Three Methods of Natural Selection
1. Directional Selection- favours individuals at one end of the phenotypic range
2. Disruptive Selection- favours individuals at both extremes of the phenotypic ranges
3. Stabilizing Selection- favours intermediate variants and acts against extreme
phenotypes
Natural selection favours certain heritable traits through differential reproductive success
Why Not Perfect Organisms?
1. Evolution is limited by historical constraints
2. Adaptations are often compromises because organisms must do many things
3. Chance, environment and natural selection intact
4. Selection can only edit existing variations
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Document Summary

The evolution of similar or analogous features in distantly related groups. Analogous traits arise when groups independently adapt to similar environments in different ways. Natural selection *observations: there is a difference in phenotypes for most characters in a population, there traits come from the parents, overproduction of offspring is frequently seen in nature, only lucky few offspring will mature and reproduce. Natural selection- cautions: survival of the fittest- evolution operates on populations, only heritable traits are passed on, may be suitable for one environment. Populations= a localized group of individuals that belong to the same species. Species= a group of organisms that possess similar characteristic and can interbreed. Microevolution is a change in allele frequencies in a population. Population genetics *sources of genetic variation & changes in allele frequency* Sources of genetic variation: mutation, point mutations, alterations of gene number or sequence, sexual reproduction, crossing over b, fertilization.

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